Deceiving trial period

I registered for the 7 day trial for Rain and the connection was terrible, since the SIM card would just stop working at times. When I tried to cancel the SIM card, it would not allow me to, even though I had tried to do so on multiple occasions. Only after the 7 day trial period was up, did the website allow me to cancel my sim card and thus Rain will charge me the full amount for the next month.